What is EFW steel pipe

EFW steel pipe(Electric Fusion Welding steel pipe) refers to an electron beam welding, the use of high-speed movement of the electron beam directed impact kinetic energy is converted to heat the workpiece so that the workpiece leaving the melt, the formation of the weld. EFW steel pipe is formed by rolling plate and welding the seam. The weld flash can be removed from the outside or inside surfaces using a scarfing blade. The weld zone can also be heat treated to make the seam less visible. Welded pipe often has tighter dimensional tolerances than seamless, and can be cheaper if manufactured in the same quantities. It is mainly used for welding dissimilar steel welding sheet or which high power density, metal weldment can rapidly heated to high temperatures, which can melt any refractory metals and alloys. Deep penetration welding fast, heat-affected zone is extremely small, so small performance impact on the joints, the joint almost no distortion. But it has a requirement on a special welding room because welding using X-rays.

Materials of EFW steel pipe

Pipes made from carbon steel lose strength at high temperatures. Electric-resistance-welded pipe is not considered satisfactory for service above 750 F, whereas furnace-buttwelded pipes are not good above 650 F. For higher temperatures, pipe made from stainless steels or other alloys should be considered.

Pressure ratings for steel pipe at different temperatures are calculated according to the ANSI B31.3 Code for Pressure Piping. ANSI B31.3 gives stress temperature values for the various steels from which pipe is fabricated.

Seam Welded Pipes are made using plates while Seamless pipes are made using dies. Steel pipes are commonly made with Black Finish or Galvanized. Proper selection of steel pipe material is critical for strength and durability required for application and ductility and machinability required to join it and form into piping. The selected pipe must withstand the conditions of use, especially pressure, temperature and corrosion conditions.

All these requirements can be met by selecting a pipe made to an appropriate standard e.g. ASTM or API Standard.

ASTM A-53

One of the two most used steel pipe material for welding, bending and coiling.

Wall thicknesses are mainly Sch 40 (STD) and Sch 80 (XS).

They are either made seamless or seamed using ERW, in Grades A and B. Grade B has higher tensile strength.

Used mainly for utility services. For process piping, A106 is used.

NPS 1⁄8 to NPS 26 [DN 6 to DN 650].

Temperature Range : -15 to 415 deg.C.

There are three types and 5 Grades as shown below.

Type S : Seamless Pipe with Grade A and B based on Carbon Content. A: 0.25% and Grade B : 0.3 Percent. Use A if bending and Closed Coiling to be done. Currently an outdated specification and has been replaced by ASTM A106 specification for seamless carbon steel pipe.

Type E : Electric Resistance Welded with Grade A and B based on Carbon Content. A:0.25% and Grade B: 0.3 Percent. Use A if bending and Closed Coiling to be done.

ASTM A-106

This is a seamless carbon steel pipe for high-temperature service in NPS 1⁄8 to NPS 48 inclusive, with nominal (average) wall thickness as given in ANSI B 36.10.

They are mainly used for Process piping while A53 Used for Utility services.

Temperature Range : -15 to 415 deg.C.

Pipe ordered under this specification shall be suitable for bending, flanging, and similar forming operations, and for welding.

Available grades are Grade A, B and C, with carbon content 0.25, 0.3 and 0.35 respectively. Hardness increases and weldability decreases. Bending ability also decreases from A to C.

Grade A rather than Grade B or Grade C is the preferred grade for close coiling or cold bending.

Wall thicknesses are mainly Sch 40 (STD) and Sch 80 (XS). They are either made seamless or seamed using ERW.

ASTM A-120

This is the most widely stocked pip. It covers welded and seamless steel pipe for normal use in steam, water, and gas (including air) service. This pipe is not intended for bending, coiling or high temperature service. It is not specified for hydrocarbon process lines.

ASTM A-672

API 5L : Line Pipe

In the oil and natural gas industries, steel pipe used to convey oil and gas is manufactured to the American Petroleum Institute’s standard API 5L, which applies tighter control of composition and more testing than ASTM-120. Available Grades are :

Grade A and B SMLS,

Grade A and B ERW,

Grade FBW

ASTM A312 Stainless Steel

This is a seamless, straight-seam welded, and heavily cold worked welded austenitic stainless steel pipe intended for high-temperature and general corrosive service. Chromium content ranges from 15 to 26 Percent.

ASTM A333 : LTCS

This is a low temperature carbon steel material used for operating temperatures in range of -15 deg C to -100 deg. C. Both Seamless and Welded Steel pipes are available. These pipes require Impact Testing. Grade 1 and Grade 3 are mostly used. No filler metal is used in welding operation. All pipes shall be heat treated to control their microstructure.

ASTM A335 : Alloy Steel

This is a seamless ferritic alloy steel pipe intended for elevated temperature service, more than 415 deg.C and upto 600 deg.C.

Pipe ordered to this specification shall be suitable for bending, flanging (vanstoning), and similar forming operations, and for fusion welding. These are seamless pipe only.

Available grades are : P1,P2,P5,P5B, P5C,P9,P11,P12,P15,P21,P22,P23,P91,P122,P911

ASTM A672 standard specification for electric fusion welded steel pipe for high pressure service at moderate temperatures.This specification covers electrical-fusion-welded steel pipe for high-pressure service at moderate temperatures. Heat treatment may or may not be required to attain the desired properties or to comply with applicable code requirements. An analysis of each mill heat of plate material shall be made, also, an analysis of the finished deposited weld material from each 500 ft or fraction thereof shall be made. The mechanical test requirements includes one tension test specimen to represent each lot of finished pipe, and one transverse-guided-weld-bend test (two specimens) to represent each lot of finished pipe. Also, radiographic examination shall be made on the full length of each weld.

Chemical Requirements of ASTM A672 :

Specification

Steel grade

Chemical composition

Remarks

C

Si

Mn

P

S

Ti

Pipes for pressure service ASTM A671, A672

-/A45

-/0.17

–

0.98

0.035

0.035

–

A671/A672

-/A50

-/0.22

–

CA55/A55

0.28

–

-/B55

-/0.20

0.13~0.45

CB60/B60

0.24

CB65/B65

0.28

CB70/C70

0.31

1.30

-/C55

-/0.18

0.55~0.98

CC60/C60

0.21

CC65/C65

0.24

0.79~1.30

CC70/C70

0.27

Mechanical Properties of ASTM A672:

Products

Steel Grade

BASE METAL MECHANICAL COMPOSITION

Welding point tensile strength (N/mm2)

Remarks

Yield point (N/mm2)

Tensile Stregth (N/mm2)

Test Pieces

Elongation (%)

Pipes for pressure service ASTM A671, A672

-/A45

-/165

-/310~450

–

-/30

-/310~450

A671/ A672

-/A50

-/185

-/345~485

-/28

-/345~485

CA55/A55

205

380~515

27

380~515

-/B55

-/205

-/380~515

-/27

-/380~515

CB60/B60

220

415~550

25

415~550

CB65/B65

240

450~585

23

450~585

CB70/B70

260

485~620

21

485~620

-/C55

-/205

-/380~515

-/27

-/380~515

CC60/C60

220

415~550

25

415~550

CC65/C65

240

450~585

23

450~585

CC70/C70

260

485~620

21

485~620

API 5L

EFW Pipe

Tolerance of Outside Diameter

Standard

Out Diameter

Tolerance of Pipe End

Tolerance of Pipe Body

API 5L

219.1～273.1

+1.6mm, -0.4mm

±0.75%

274.0～320

+2.4mm, -0.8mm

±0.75%

323.9～457

+2.4mm, -0.8mm

±0.75%

508

+2.4mm, -0.8mm

±0.75%

559～610

+2.4mm, -0.8mm

±0.75%

Tolerance of Wall Thickness

Standard

Grade

Out Diameter

Wall Thickness

API 5L

A

219.1～457

+15%, -12.5%

B

508～610

+17.5%, -12.5%

X42-X80

508～610

+19.5%, -8%

Chemical Analysis and Mechanical Properties

Standard

Class

Grade

Chemical Analysis(%)

Mechanical Properties(min)(Mpa)

C

Mn

P

S

Tensile Strength

Yield Strength

API 5L

PSL1

B

0.26

1.20

0.030

0.030

414

241

X42

0.26

1.30

0.030

0.030

414

290

X46

0.26

1.40

0.030

0.030

434

317

X52

0.26

1.40

0.030

0.030

455

359

X56

0.26

1.40

0.030

0.030

490

386

X60

0.26

1.40

0.030

0.030

517

414

X65

0.26

1.45

0.030

0.030

531

448

X70

0.26

1.65

0.030

0.030

565

483

PSL2

B

0.22

1.20

0.025

0.015

414

241

X42

0.22

1.30

0.025

0.015

414

290

X46

0.22

1.40

0.025

0.015

434

317

X52

0.22

1.40

0.025

0.015

455

359

X56

0.22

1.40

0.025

0.015

490

386

X60

0.22

1.40

0.025

0.015

517

414

X65

0.22

1.45

0.025

0.015

531

448

X70

0.22

1.65

0.025

0.015

565

483

X80

0.22

1.85

0.025

0.015

621

552

High-frequency straight seam electric-resistance welded steel pipe(erw steel pipe) is hot-rolled coil after forming machine, the use of high-frequency current skin effect and proximity effects, the tube edge heating and melting, squeeze roller under pressure welding to achieve production.High-frequency resistance welding steel pipe, welding pipe and ordinary welding process is not the same, the weld is made of the base metal melt from the body, the mechanical strength is better than the general pipe. Smooth appearance, high precision, low cost weld high and small, favorable 3PE anti-corrosion coating. There are significant differences in the welding methods between high frequency welded pipe and submerged arc welded pipe. As the welding is done instantly at high speed, the difficulty of ensuring the quality of welding is much higher than that of submerged arc welding.

ERW Casing

Standard: API SPEC 5CT

Application: Casing serves as wall of well

Specification

OD

WT

End Type

inch

mm

inch

mm

Grade

J55

M65

N80/L80-1

P110

K55

8 5/8

219.08

0.304

7.72

–

PS

–

–

0.352

8.94

PSLB

PSLB

–

–

0.400

10.16

PSLB

PSLB

PLB

PLB

0.450

11.43

–

PLB

PLB

PLB

0.500

12.70

–

–

PLB

PLB

9 5/8

244.48

0.352

8.94

PSLB

PSLB

–

–

0.395

10.03

PSLB

PSLB

PLB

PLB

0.435

11.05

–

PLB

PLB

PLB

0.472

11.99

–

PLB

PLB

PLB

0.545

13.84

–

–

PLB

PLB

10 3/4

273.05

0.350

8.89

PSB

PSB

–

–

0.400

10.16

PSB

PSB

–

–

0.450

11.43

PSB

PSB

PSB

PSB

0.500

12.57

–

PSB

PSB

PSB

0.545

13.84

–

–

–

PSB

13 3/8

339.72

0.380

9.65

PSB

PSB

–

–

0.430

10.92

PSB

PSB

–

–

0.480

12.19

PSB

PSB

PSB

PSB

0.514

13.06

–

–

PSB

PSB

16

406.40

0.438

11.13

PSB

–

–

–

0.495

12.57

PSB

–

–

–

0.656

16.66

P

–

–

–

18 5/8

473.08

0.435

11.05

PSB

–

–

–

20

508

0.438

11.13

PSLB

–

–

–

0.500

12.70

PSLB

–

–

–

0.635

16.13

PSLB

—

–

–

Dimensional Tolerance

Standard

Tolerance of O.D.

Tolerance of W.T.

Straightness of Pipe Body

Straightness of Pipe End

Tolerance for Weight

API 5CT

+1%, -0.5%

-12.5%

≤0.2%L

≤3.18mm

+6.5%, -3.5%

Mechanical Properties

Standard

Grade

Yield Strength(Mpa)

Tensile Strength(Mpa)

Hardness(HRC)

Impact Energy(J)(min)

Impact Temperature(℃)

API 5CT

J55

379-552

≥517

–

T-10-20(SR16)

21

K55

379-552

≥655

–

L-10-27(SR16)

M65

448-586

≥586

≤22

T-10-20, L-10-41

C19-20, C76-77(SR16)

0

L80

552-655

≥655

≤23

N80

552-758

≥689

–

P110

758-965

≥862

–

Chemical Composition(%)

Standard

Grade

C

Mn

P

S

Ni

Cu

Si

API 5CT

J55

–

–

≥0.030

≥0.030

–

–

–

K55

–

–

≥0.030

≥0.030

–

–

–

M65

–

–

≥0.030

≥0.030

–

–

–

L80

≥0.43

≥1.90

≥0.030

≥0.030

≥0.25

≥0.35

≥0.45

N80

–

–

≥0.030

≥0.030

–

–

–

P110

–

–

≥0.030

≥0.030

–

–

–

EFW Pipe Manufacturing Process

In EFW welding process, the external high energy electric arc is used to create a weld joint. Once the welding is done, the excess weld material from outside and inside of the pipe is removed with the help of trimmer tools.

In general, to reduce the negative effect of welding, a localized heat treatment of weld seam is carried out immediately it clears online ultrasonic test. Normally an induction heating method is used to restore microstructure of welded zone. These type of heat treatment is known as post annealing. In next stage, the pipe will go through Hydro testing, visual and dimensional inspection and once certified by inspection engineer it will send for packaging.

For pipes or tubes size 4 inch (10.2mm) OD and below, strip is fed into a set of forming rolls which consists of horizontal and vertical rollers so placed as to gradually from the flat strip in to a tube which is then allowed to pass the welding electrodes. The electrodes are copper disks connected to the secondary of a revolving transformer assembly.

The copper disk electrodes make contact on each side of the seam and temperature is raised to the welding point. Outside flash is removed by a cutting tool as the tube leaves the electrodes, inside flash is removed either by an air hammer or by passing a mandnel through the welded tube after the tube has been cooled.

This is termed as Electric Resistance welded or ERW tube/pipe. If this ERW is being drawn further to get desired size of tubes or pipes, in cold condition is called as Cold Drawn welded or CDW.

ERW pipes means Electric Resistance Welded Pipes

SAW – Submerged Arc Welded

This process is used for pipes from 24″ to 36″ i.e 610mm to 914mm OD. Flat plate is first pressed into U and later O shape.

The O shape is placed in an automatic welder and backed up on the inside by a water cooled copper shoe. Two electrodes in close proximity and used. The electrodes are not in actual contact with the pipe. The current passes from on electrode through a granular flux and across the gap in the pipe to the second electrode. The high temperature of the arc heats the edges of the plate, a welding rod placed just over the seam is thereby melted and metal is deposited in the groove.